Differential induction of peroxygenase-dependent microsomal aniline hydroxylase by chronic ethanol ingestion.
The liver microsomal-mediated hydroxylation of aniline, which is selectively induced by chronic (EtOH) ingestion, has been studied as a function of NADPH plus dioxygen (O2)- or hydroperoxide-dependent reactions. Consistent with the well-documented induction of aniline hydroxylase following chronic ethanol -ingestion, the results showed selectivity towards aniline hydroxylase by the NADPH plus O2- and tert-butyl hydroperoxide (t-BuOOH)-dependent reactions with microsomes from EtOH-fed rats. On the other hand, the cumene hydroperoxide (CumOOH)-dependent aniline hydroxylase activity was not discriminated between microsomes from EtOH- and pair-fed rats. In parallel experiments with positive controls, CumOOH did show selectivity for phenobarbital (PB)-induced microsomal aniline hydroxylase compared to chow-fed rats. The Kcat/KM values, which indicate the efficiency of enzyme catalysis, for NADPH plus O2-, t-BuOOH, and CumOOH-dependent aniline hydroxylase from EtOH-fed rats were 102, 37, and 5 and from pair-fed rats were 68, 4, and 4 (nmol p-aminophenol/min/nmol cytochrome P-450)/mM aniline, respectively. The relative Kcat/KM ratio for EtOH-fed to that of pair-fed microsomal aniline hydroxylase from NADPH plus O2-, t-BuOOH-, and CumOOH-dependent reactions were 1.5, 7.4, and 1.2, respectively. The present preliminary studies indicate that the catalytic efficiency of EtOH-induced aniline hydroxylase is significantly greater for the t-BuOOH-dependent reaction.
Narayan
S
S
Department of Biochemistry, Louisiana State University, Baton Rouge 70803.
Bounds
P L
PL
Winston
G W
GW
D000814:Aniline Compounds / Q000378:metabolism; D000815:Aniline Hydroxylase / Q000096:biosynthesis*; D000818:Animals; D001555:Benzene Derivatives / Q000494:pharmacology; D004334:Drug Administration Schedule; D004790:Enzyme Induction; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D010545:Peroxides / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D020122:tert-Butylhydroperoxide
D000814:Aniline Compounds; D001555:Benzene Derivatives; D010545:Peroxides; D000431:Ethanol; D009249:NADP; D020122:tert-Butylhydroperoxide; D010544:Peroxidases; D010105:Oxygenases; D000815:Aniline Hydroxylase; C007164:cumene hydroperoxide; D010100:Oxygen; C023650:aniline